1. Field of the Invention
This invention relates to a radio apparatus which is used in a base station in a mobile telephone system and which has receiving/sending equipment and an antenna, in particular, to a method of controlling the radio apparatus in which the receiving/sending equipment and an antenna are disposed apart from each other.
2. Description of the Related Art
In general, a mobile telephone system has a plurality of base stations and a great number of mobile stations communicable with the base station or stations. In this event, each of the base stations is structured by a transmitter/receiver and an antenna unit which is remote from the transmitter/receiver by several meters or so and which is connected to the transmitter/receiver through a cable, such as a coaxial cable. The transmitter/receiver is located indoors while the antenna unit is placed outdoors .
Under the circumstances, it is necessary to detect, on a side of the transmitter/receiver, failure or trouble which might occur in the antenna unit. To this end, a failure detection circuit is usually included in the transmitter/receiver of each base station to detect the failure or the trouble in the antenna unit and to produce an alarm on detection of such failure or trouble.
However, it has been found out that such a failure detection circuit can not correctly detect the failure or trouble in the antenna unit. This is because the antenna unit is distant from the transmitter/receiver, which causes a standing wave to occur on the cable between the antenna unit and the transmitter/receiver.
Specifically, occurrence of the standing wave might often result in wrong detection of the failure or trouble in the antenna unit, since the standing wave has, at a demodulating point, a node at which the standing wave becomes the smallest in amplitude.
Therefore, it is an object of the invention to solve the above problem.
It is also another object of the invention to provide a radio apparatus and method of controlling the radio apparatus which can accurately detect trouble of the antenna apparatus which is disposed apart from the receiving/sending apparatus and troubles of connecting between thereof, efficiently send a signal, and protect the sending apparatus when the troubles occur.
According to a first aspect of the invention, there is provided a radio apparatus including an antenna unit which radiates a transmission signal and a transmitter unit which supplies the transmission signal to the antenna unit through a line between the transmitter unit and the antenna unit. Here, the antenna unit comprises a coupler which partially extracts the transmission signal to produce an extracted signal and a rectifying circuit which rectifies the extracted signal into a d.c. component signal and superposes the d.c. component signal on the transmission signal. On the other hand, the transmission unit comprises a separating circuit which separates the d.c. component signal from the transmission signal.
According to a second aspect of the invention, the rectifying circuit includes a detector which rectifies the extracted signal into the d.c. component signal.
According to a third aspect of the invention, the rectifying circuit includes a first coil which superposes the d.c. component signal on the transmission signal.
According to a fourth aspect of the invention, the separating circuit includes a second coil which separates the d.c. component signal from the transmission signal.
According to a fifth aspect of the invention, the transmitter unit includes a control circuit which compares the d.c. component signal separated from the transmission signal with a predetermined reference signal and detects trouble when the d.c. component signal is lower than the predetermined reference signal.
According to a sixth aspect of the invention, the control circuit further decreases the power of the transmission signal when the d.c. component signal as lower than the predetermined reference signal.
According to a seventh aspect of the invention, the transmitter unit further comprises a variable attenuator which varies the power of the transmission signal and an arithmetic circuit which controls the variable attenuator based on a voltage level of the d.c. component signal separated from the transmission signal.
According to an eighth aspect of the invention, the transmitter unit further comprises a matching circuit which matches an impedance of the transmitter unit to that of the antenna unit and a matching control circuit which controls the matching circuit based on a voltage level of the d.c. component signal separated from the transmission signal.
According to a ninth aspect of the invention, the transmitter unit includes a control circuit which determines whether or not the d.c. component signal which is separated from the transmission signal falls within a predetermined range and detects trouble when the d.c. component signal does not fall within the predetermined range.
According to a tenth aspect of the invention, there is provided a method of controlling a radio apparatus including an antenna unit which radiates a transmission signal and a transmitter unit which supplies the transmission signal. Here, the antenna unit and the transmitter unit being connected electrically from each other, and the method comprises the steps of partially extracting, at the antenna unit, the transmission signal, rectifying, at the antenna unit, the extracted signal into a d.c. component signal, superposing, at the antenna unit, the d.c. component signal on the transmission signal, and separating, at the transmitter unit, the d.c. component signal from the transmission signal.
According to an eleventh of the invention, there is provided a method of controlling an antenna unit remote from a transmitter unit. Here, the antenna unit which radiates the transmission signal and the transmitter unit which whiles the transmission signal are included in a radio apparatus and connected electrically from each other, and the method comprises the steps of partially extracting the transmission signal, rectifying the extracted signal into a d.c. component signal, and superposing the d.c. component signal on the transmission signal.
According to a twelfth of the invention, there is provided a method of controlling a transmitter unit. Here, the transmitter unit which supplies a transmission signal and an antenna unit which radiates the transmission signal are included in a radio apparatus and connected electrically from each other, and the method comprises the step of receiving a d.c. component signal via the transmission signal from the antenna unit and separating the d.c. component signal from the transmission signal.
According to a thirteenth of the invention, the method further comprises the steps of comparing the d.c. component signal which is separated from the transmission signal with a predetermined reference signal and detecting trouble when the d.c. component signal is lower than the predetermined reference signal.
According to a fourteenth of the invention, the method further comprises the step of decreasing the power of the transmission signal when the d.c. component signal is lower than the predetermined reference signal.
According to a fifteenth of the invention, the method further comprises the steps of varying the power of the transmission signal based on a voltage level of the d.c. component signal separated from the transmission signal and controlling intensity of the transmission signal which is radiated from the antenna unit so that the intensity may be equal to a predetermined value.
According to a sixteenth of the invention, the method further comprises the step of controlling matching of an impedance of the transmitter unit to that of the antenna unit so that a voltage level of the d.c. component signal separated from the transmission signal may become maximum.
According to a seventeenth of the invention, the method further comprises the step of determining whether or not the d.c. component signal which is separated from the transmission signal falls within a predetermined range and detecting trouble when the d.c. component signal does not fall within the predetermined range.